Clinical Assessment of a Novel Microprobe Array Continuous Glucose Monitor for Type 1 Diabetes

Continuous knowledge of ambient glucose levels will be of benefit to patients with T1DM, especially those with troublesome hypoglycaemia. Existing monitors require skin puncture to access interstitial fluid and sense its glucose content. Despite their clinical benefits, their use is associated with discomfort and their accuracy is questionable in hypoglycaemia. The development of a painless continuous glucose monitor is regarded as the top research priority by patients with diabetes. A novel continuous glucose monitoring device has been developed at Imperial College based on microprobe technology. It consists of a small, wearable patch (~1 cm2), the size of a conventional postage stamp, containing microscopic projections (microprobes) that penetrate only the outermost skin layer. It accesses interstitial fluid to sense its glucose content without stimulating skin nerve fibres or reaching blood vessels within skin layers. The microprobe surface has the consistency of sandpaper. It is pushed into the skin with an applicator allowing it to penetrate through the skin layers and access the interstitial fluid in a minimally invasive manner. The device is disposable and optimum performance will be assessed over five days. The advantages of microprobe technology have been demonstrated in other clinical situations and include painless insertion, absence of bleeding and a low infection risk. The large surface area utilised in our microprobe device has the potential to improve device sensitivity and accuracy. Pre-clinical validation tests have demonstrated the ability of the device to respond accurately to variable glucose concentrations and to penetrate the outermost skin layer without fracture. We aim now to further develop the device through clinical studies in non-diabetic subjects and subjects with type 1 diabetes to allow painless accurate continuous glucose monitoring.

The study will recruit 16 non-diabetic subjects and 20 subjects with type 1 diabetes.

It will be conducted over four phases;

oPhase 1 will assess safety, as a primary outcome, and efficacy, as a secondary outcome, in non-diabetic subjects over six hours in the clinical research facility where the device will be fitted and a cannula inserted for venous sampling every 15 minutes to measure venous blood glucose (YSI). Safety will be assessed with regards to skin inflammation and pain. Efficacy will be assessed in this phase by assessing magnitude of current measured by the microprobe array sensor and comparison of measured ISF glucose concentrations to simultaneous venous blood glucose samples (YSI).

oPhase 2 will also assess safety, as a primary outcome, and efficacy, as a secondary outcome, in non-diabetic subjects over a period of 24 hours. The first six hours in the clinical research facility (same as phase 1), then subject will be allowed to go home with the device to assess safety over that period.